As a general guideline, with numerous exceptions:
Top 2 is worth a bet (pot). If you get raised, muck easily unless you have quite a redraw with it.
If someone pots to you, it's usually also worth a call but not a raise, but it depends on opponent--namely if they'll pot a draw. If they'll only pot a set, then just muck it.
Anything less than top 2 should just go to the muck.